The present invention relates to internal combustion engines; more particularly, to devices for controlling the variable activation of intake valves in an internal combustion engine; and most particularly, to a system for controllably activating and deactivating a finger follower for a double-lobed cam in an internal combustion engine between high valve lift and low valve lift modes.
Internal combustion engines are well known. In an overhead valve engine, the valves may be actuated directly by camshafts disposed on the head itself, or the camshaft(s) may be disposed within the engine block and may actuate the valves via a valve train which may include valve lifters, pushrods, and rocker arms.
It is known that for a portion of the duty cycle of a typical multiple-cylinder engine, the performance load can be met by a functionally smaller engine having fewer firing cylinders, and that at low-demand times fuel efficiency can be improved if one or more cylinders of a larger engine can be withdrawn from firing service. It is also known that at times of low torque demand, valves may be opened to only a low lift position to conserve fuel, and that at times of high torque demand, the valves may be opened wider to a high lift position to admit more fuel. It is known in the art to accomplish this by de-activating a portion of the valve train associated with pre-selected cylinders in any of various ways, such as by providing a special cam finger follower having a latching pin or slide which may be activated and/or deactivated electromechanically. The cam finger follower is so configured that it causes no lift (with a single-lobed cam) or low lift (with a double-lobed cam) of the valve when the pin is disengaged, and high lift of the valve when the pin is engaged.
Various methods for actuating this type of latching pin or slide are known. For example, U.S. Pat. No. 5,544,626 discloses a hydraulic apparatus and return spring for latching and delatching a latching pin. The latching pin is disposed in, and extends from, a bore in an outer finger arm which is supported by a hydraulic lash adjuster. When moved radially inwards of the outer finger arm, the pin engages an inner finger arm which is supported by the valve stem. When valve deactivation is desired, engine oil pressure supplied to the apparatus is increased to approximately 50 psi, which is sufficient to overcome the force of the return spring and move the latching pin out of engagement with the inner finger arm. The outer finger arm continues to follow the surface of the single-lobed camshaft, but the cam motion is not translated to the inner finger arm, so the valve is not actuated thereby.
Alternatively, the pin may be engaged and disengaged by the direct action of an electric solenoid axially disposed at the outer end of the pin. For example, U.S. Pat. No. 5,653,198 discloses a latching pin engaged by a rotary or linear solenoid and disengaged by a return spring.
The disclosed linkages have several shortcomings, an important one of which is that the solenoids physically reside inside the cam cover of the engine. Therefore, the solenoids, connectors, and wiring components are exposed to high temperature engine oil which can be detrimental to connection reliability. It can be necessary to employ special insulation and sealing schemes to protect the components and connections from failure. Despite such special measures, it should be expected that such deactivation systems will experience an unacceptably high failure rate.
Further, a wiring harness is required to protect and organize the individual wires leading to the various solenoids, as well as a sealed port for the wiring harness to pass through the cam cover. The wiring harness is thus exposed to hostile conditions within the valve actuation chamber of the cam cover, making it prone to electrical failure.
Further, placing the solenoid actuator in a plane transverse of the engine and containing the finger follower and valve can cause the spark plug and plug well in the engine head to be displaced axially to a less desirable location along the head.
It is a principal object of the present invention to provide an improved apparatus for electromechanically actuating and deactuating the latching pin of a cam finger follower wherein the electromechanical portion of an actuating solenoid is mounted on the outside of the cam cover.
It is a further object of the invention to provide such apparatus wherein the actuating stroke of the solenoid may be offset from the axis of the latching pin to permit optimum placement of the spark plug within the cylinder head.
It is a still further object of the invention to provide such apparatus wherein the need for a separate wiring harness for all the pin-actuating solenoids on an engine is obviated.
Briefly described, a control system for variable activation of intake valves in an internal combustion engine in accordance with the invention includes a linear solenoid disposed on an outer surface of the intake valve cam cover and having the solenoid""s armature extending through a sealing port in the cam cover into the valve actuation chamber. A bellcrank is mounted to the cam cover within the actuation chamber between the solenoid armature and the latching pin of a variable valve actuation apparatus such that energizing and de-energizing of the solenoid causes corresponding actuation and de-actuation of the latching pin. Preferably, for a plurality of such systems on an individual engine, the solenoids are provided with connecting pins on an upper surface thereof and are held in place by a formed plastic retainer, preferably containing an overmolded wiring bundle having exposed connectors placed to mate with the solenoid pins to automatically connect the embedded wiring harness properly to each solenoid upon installation of the retainer onto the engine.